The present invention relates to a wear resistant low friction coating for a glass run channel or the like and a method for providing such a coating on a glass run channel. More particularly, the present invention relates to a thermoplastic discontinuous coating for a glass run channel.
Low friction coatings such as flocks and polytetrafluoro ethylene coatings are known in the art for providing reduced resistance at contact points between windows and glass run channels. While such coatings are suitable for reducing friction between the rubber glass run and the window, such coatings do not have good wear resistant characteristics as load bearing surfaces.
A particular problem in glass run channel applications has been wear through at the base of the glass run channel. Therefore, it has been a goal in the art to provide some mechanism for reducing wear at the base of a glass run channel to thereby increase the life of glass run channels in vehicle applications.
One such structure is shown in U.S. Pat. Nos. 4,923,759; 4,913,976; and 5,013,379. These patents teach the co-extrusion of a polypropylene wear strip at the base of a glass run channel, which is melt bonded to an EPDM rubber. In these patents a cooling flow of air is utilized to maintain a consistent flat surface on the polypropylene thermoplastic wear strip during co-extrusion. The layer taught in this particular patent is a rather thick (0.075) inch layer of polypropylene, which reduces flexibility of the weatherstrip. The above patents also have the disadvantage in that the resultant wear strip which is produced has a smooth wear surface. This smooth surface increases the friction between the edge of the window and the glass run channel and thus, is an undesirable side effect even though increased longevity of the base of the glass run channel may be achieved.
Thus, it has been a goal in the art to provide a wear surface which would increase the longevity of a glass run channel and would also have a reduced coefficient of friction, thereby providing an improved coating for a glass run channel.